וְהֵסִ֩ירָה֩ אֶת־שִׂמְלַ֨ת שִׁבְיָ֜הּ מֵעָלֶ֗יהָ וְיָֽשְׁבָה֙ בְּבֵיתֶ֔ךָ וּבָֽכְתָ֛ה אֶת־אָבִ֥יהָ וְאֶת־אִמָּ֖הּ יֶ֣רַח יָמִ֑ים וְאַ֨חַר כֵּ֜ן תָּב֤וֹא אֵלֶ֙יהָ֙ וּבְעַלְתָּ֔הּ וְהָיְתָ֥ה לְךָ֖ לְאִשָּֽׁה׃
at huhubarin niya ang kasuotan ng kanyang pagkabihag, at mananatili siya sa iyong bahay at tatangisan niya ang kanyang ama at ang kanyang ina nang isang buong buwan; at pagkatapos niyon ay maaari kang sumiping sa kanya at maging kanyang asawa, at siya ay magiging iyong asawa.
Rashi
והסירה את שמלת שביה AND SHE SHALL REMOVE THE RAIMENT OF HER CAPTIVITY — the reason is because these are fine clothes, for the women of the heathen peoples adorned themselves in time of war in order to lure others (the enemy) to unchastity with them (Sifrei Devarim 213:1).
Bekhor Shor
And she shall weep for her father and her mother. This is not a mitzvah, just that certainly she would cry. One says (Yevamot 48b) that it is her actual father, and one says, idolatry, as it says (Yirmiyahu 2:27) "They say to a tree: You are my father". And after that, come upon her but before this, no; since this thing is not seemly, that she is weeping and you are sporting with her.
Chizkuni
והסירה את שמלת שביה, “and she is to remove the outer garment she wore when taken prisoner;” this was a garment she wore while worshipping her idols. We have examples in the Bible of such garments having to be scrapped in Genesis 35,2, where Yaakov commands his family members to scrap the captured garments they were wearing, which had originated in the city of Sh’chem. Anything that she was able to remove, which was a reminder of when she worshipped idols, had to be removed and destroyed.